window.onload = function(){
  const navigate = document.querySelector('#navigate')
  window.addEventListener('scroll',()=>{
    if (document.documentElement.scrollTop > 80){
      navigate.classList.add('fixed-top')
      navigate.classList.add('bg-dark')
      navigate.classList.remove('bg-transparent')
    }
    else{
      navigate.classList.remove('fixed-top')
      navigate.classList.remove('bg-dark')
    }
  })
}